a) Technical Field
The invention can be used in the most varied branches of industry for measuring lengths, distances and speeds. The inventive carrier frequency interferometer can be used with particular advantage where high object speeds, e.g. rotary and translatory movements occur on ultraprecision working machines in the case of high incremental resolutions.
b) Prior Art
Leading measurement system manufacturers traditionally use asymmetrical carrier frequency interferometers (SPIE, vol. 480, pp 78-83, May 1984; U.S. Pat. No. 47 11 547; U.S. Pat. No. 47 52 133). As a result of the asymmetry, the reference and measurement channels have a different temperature dependency, which makes them unsuitable for nanometer measurement systems. The diagonal beam emergence of the measurement beam relative to the reference beams does not make it possible to position the reference mirror outside or above the movement path of the measurement mirror. As a result of return intensity into the light source, its stability is impaired. Possible tilting of the primary beam leads to divergences of the measurement and reference beams, which once again influence the measuring signal.